There is class of devices, based on the use of a membrane, that has been used for plasmapheresis, that is separating plasma from whole blood. More specifically, this type of device employs relatively rotating surfaces, at least one or which carries a porous membrane. Typically the device employs an outer stationary housing and an internal spinning rotor covered by a porous membrane.
One such well-known plasmapheresis device is the Autopheresis-C® separator available from Fenwal, Inc., a Fresenius Kabi company, of Lake Zurich, Ill. A detailed description of a spinning membrane separator may be found in U.S. Pat. No. 5,194,145 to Schoendorfer, which is incorporated by reference herein. This patent describes a membrane-covered spinner having an interior collection system disposed within a stationary shell. Blood is fed into an annular space or gap between the spinner and the shell. The blood moves along the longitudinal axis of the shell toward an exit region, with plasma passing through the membrane and out of the shell into a collection bag. The remaining blood components, primarily red blood cells, platelets and white cells, move to the exit region between the spinner and the shell and then are typically returned to the donor.
Spinning membrane separators have been found to provide improved plasma filtration rates, due primarily to the unique flow patterns (“Taylor vortices”) induced in the gap between the spinning membrane and the shell. The Taylor vortices create shear forces in the gap that help to keep the blood cells from depositing on and fouling or clogging the membrane, which otherwise would tend to decrease the rate of fluid flow through the membrane, thus increasing procedure times, and increase the transmembrane pressure, which could cause cell damage or device failure. Nevertheless, fouling or clogging of the membrane continues to be a limiting factor in efficiently performing plasmapheresis, and various methods for controlling fouling have been contemplated, including by optimizing the filtrate flow rate. See, e.g., US 2012/0273416, which is incorporated by reference herein.
The subject matter disclosed herein provides further advances in controlling the fouling or clogging of membrane separators for performing plasmapheresis.